Background
Coronavirus disease 2019 (COVID-19) is a pandemic with no specific antiviral treatments or vaccines. There is an urgent need for exploring the neutralizing antibodies from patients with different clinical characteristics.
Methods
A total of 117 blood samples were collected from 70 COVID-19 inpatients and convalescent patients. Antibodies were determined with a modified cytopathogenic neutralization assay (NA) based on live severe acute respiratory syndrome coronavirus 2 and enzyme-linked immunosorbent assay (ELISA). The dynamics of neutralizing antibody levels at different time points with different clinical characteristics were analyzed.
Results
The seropositivity rate reached up to 100.0% within 20 days since onset, and remained 100.0% till days 41β53. The total geometric mean titer was 1:163.7 (95% confidence interval [CI], 128.5β208.6) by NA and 1:12β441.7 (95% CI, 9754.5β15β869.2) by ELISA. The antibody level by NA and ELISA peaked on days 31β40 since onset, and then decreased slightly. In multivariate generalized estimating equation analysis, patients aged 31β45, 46β60, and 61β84 years had a higher neutralizing antibody level than those aged 16β30 years (Ξ²β=β1.0470, Pβ
=β
.0125; Ξ²β=β1.0613, Pβ
=β
.0307; Ξ²β=β1.3713, Pβ
=β
.0020). Patients with a worse clinical classification had a higher neutralizing antibody titer (Ξ²β
=β
0.4639, Pβ
=β
.0227).
Conclusions
The neutralizing antibodies were detected even at the early stage of disease, and a significant response was shown in convalescent patients.